This invention relates to measuring apparatus and method and more particularly to means for indicating the thickness of carbon deposition on a surface as a function of time.
In the manufacture of coke the formation of carbon on the upper walls and roof is a problem. The roof carbon deposits can develop to such a degree as to block charging holes, thus restricting the flow of coal and can also build so that a leveling bar cannot fit through the oven. Furthermore, hydrocarbon gases are released from the coal during the coking cycle. These hydrocarbon gases are removed from the coke oven and formed into useful byproducts, e.g., tar. However, at times the tar is characterized by a high content of solid carbon particles, thereby rendering the tar unsaleable. These particles are the result of entrained particles and thermal cracking of the hydrocarbon gases.
The two major parameters to roof carbon formation are (1) coal quality, and (2) oven top temperature. Of the two, coal may make the most important contribution to roof carbon formation but is not a condition that is easily changed or controlled. Oven top temperature is, on the other hand, more readily controlled and has a significant effect on the formation of roof carbon. If the heating is not controlled, uniform roof carbon formation can reach unmanageable proportions.
The current methods for controlling buildup of roof carbon are: (1) mechanical--i.e., carbon cutters on the ram head on all pushers, reduction of heat to top of the oven through flue system adjustments, and punching out plugged standpipes at oven roof level; (2) chemical--i.e., carrying one empty oven in the schedule and/or decarbonizing air sprays on the ram head.
Although these procedures are presently effective for control, roof carbon buildup now becomes the criterion for coking rate. Higher coking rates, made possible through improved heating and refractories, may be limited by roof carbon control.
In order to determine the effect of the coking process variables, e.g., BUT input/hour, oven roof temperature, gas flow rate from the oven, etc., it is desirable to measure the rate of deposition of the carbon, as a function of time, during the coking cycle.